A SPECTROSCOPIC  INVESTIGATION  OF  RETRO 
GRADE  RAYS  IN  HELIUM 


BY 

WILLIAM  JACOB  JENSEN 

A.B.  Carleton  College,  1920 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  ARTS  IN  PHYSICS 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


. 


.. 


1 9 


UNIVERSITY  OF  ILLINOIS 

THE  GRADUATE  SCHOOL 

Jung 


i HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 
SUPERVISION  BY WTT.T.T ftM  JACOB  JENSEN 

ENTITLED 


RAYS  Pi  R^t.tum _ 

BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 


Recommendation  concurred  in* 


Committee 

on 

Final  Examination* 


^Required  for  doctor’s  degree  but  not  for  master’s 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/spectroscopicinvOOjens 


TABLE  OF  COD  TENTS 


I.  INTRODUCTION 

A.  Purpose  of  the  Investigation,  . . . 

B.  Historical  Review  . , 

II.  PRODUCTION  OF  RETF  . 

ill.  THE  APPARATUS 

A.  T Discharge  Tube  Proper  ...... 

B.  The  Exhaus 

C.  The  Cathode  and  the  Anodes 

D.  The  Priming  System 

u.  The  Spectroscope 

IV.  MANIPULATION 

A.  Mounting  the  Tube  

B.  Procedure  for  Priming  

C.  Qg  the  Observations  

V.  DATA 

A.  Observations 

B.  Table  for  Comparison 

VI.  CONCLUSIONS  


1 

1 

4 

4 

5 


3 


6 

6 

7 

7 

8 

9 

11 

12 


I.  INTRODUCTION 

A.  Purpose  of  the  Investigation.-  The  purpose  of  this  investi- 
gation was,  primarily,  to  study  spectroscopically  the  retrograde 
rays  obtained  in  a discharge  tube  when  helium  is  the  residual  gas, 
and  to  compare  the  same  with  a similar  study  of  the  positive  rays 
formed  in  the  same  tube.  To  this  end  Special  positive  ray  tubes 
containing  hollow  cathodes  were  constructed.  Incidental  to  this 
study  several  other  factors  presented  themselves  which,  if  time  per- 
mitted, were  to  be  investigated,  such  as  the  origin  of  the  retro- 

# 

grade  rays,  whether  they  are  present  when  the  canal  through  the 
cathode  is  closed,  the  effect  of  the  shape  of  the  vacuum  tube  upon 
the  presence  cf  the  retrograde  rays,  and  any  other  factors  that  in 
any  way  affect  the  production  of  retrograde  rays;  and,  conversely, 
the  effect  cf  the  retrogr3.de  rays  themselves  upon  the  glass  and 
metal  parts  of  the  discharge  tube. 

E.  Hist  or i c al  Re v i ew . - Positive  or  canal  rays  were  discovered 

by  Goldstein  in  1SS6.  They  have  their  origin  in  front  < e cath-  j 

ode  in  the  edge  cf  the  Crookes  dark  space,  fall  towards  the  cathode  ! 
under  the  action  of  the  electric  field,  and  attain  a high  velocity.  I 
If  openings  are  made  through  the  cathode,  the  canal  rays  stream 
through  the  openings,  or  canals,  and  appear  on  the  other  side  as 
distinct  rays  or  beams.  Because  of  these  openings,  or  canals, 
through  the  cathode,  Goldstein  called  the  beam  streaming  through 
"canal  rays”,  although  they  are  now  commonly  called  positive  rays. 
The  color  of  the  canal  ray  depends  upon  the  residual  gas,-  and  is 
generally  different  in  color  from  the  cathode  ray  for  the  same  gas.' 

Goldstein  also  observed  that  there  was  a faint  additional  beam, 
having  the  same  direction  as  the  cathode  beam,  that  seemed  to  be  a 


continual; ion  of  the  positive  ray,  though  in  the  opposite  direction. 
For  this  reason  he  called  the  rays  composing  this  beam  "retrograde 
. ....  s".  Subsequent  investigations  have -shown  t . retrograd  rays 
consist  chiefly  of  positive  ions,  molecular  in  size,  though  the  rays 
may  also  contain  negative  ions,  or  indeed  neutral  particles,  atomic 
in  size.  That  four  types  of  particles  are  present  in  the  beam  leav- 
ing the  cathode  — cathode  rays  (electrons),  positive  particles 
atomic  in  size,  and  neutral  atoms  — is  evidenced  by  the  accompany- 
ing photograph  taken  by  Professor  Uni:  13.  (Photograph  Hc..l) . 

The  exposure  was  made  in  front  c?  the  cathode,  and  shews  the  mag- 
netic and  electro-static  deflections  of  the  charged  carriers,  and 
the  undeflected  central  spot  due  to  the  neutral  particles  atomic  in 
size. 

Villard*  obtained  the  spectrum  of  hydrogen  and  oxygen  for  retro- 
grade rays  in  residual  air,  and  showed  by  the  magnetic  and  electro- 
static deflections  that  the  ray  was  made  up  chiefly  cf  positively 
charged  particles  much  heavier  than  the  negative  particles  of  the 
cathode  beam. 

rr> 

J.J.  Thomson  measured  the  magnetic  and  electrostatic  deflec- 
tions on  a phosphorescent  screen,  and  cu..  e to  the  same  conclusion  as 
Villard.  He  further  showed  that  the  intensity  of  the  phosphores- 
cence due  to  negatively  charged  particles  was  much  greater  than  that 
due  to  positively  charged  particles  for  retrograde  rays,  while  the 
opposite  was  true  for  the  ordinary  positive  or  canal  rays. 

The  difference  in  the  phosphorescence  cf  lithium  chloride  when 


* P.  Villard.  C . - H endue,  143;  pp  374—876,  Nov. 5,1806. 
3 J.J.  Thomson.  Phil.  lag.  XIV,  p 353,  1907. 


. 


. 


• I '■ 

• . 


' " 3 

struck  by  positive  rays  and  when  struck  by  cathode  rays  affords  a 
simple  way  of  investigating  the  path  of  the  retrograde  rays,  and 
the  origin  of  the  canal  rays.  Lithium  chloride  phosphoresces  a rich 
deep  red  when  positive  rays  impinge  upon  it,  and  it  gives  the  bright 
red  line  of  lithium  in  the.  spectrum.  Cathode  rays  cause  a steely 
blue  phosphorescence  which  gives  a continuous  spectrum.  By  means  of 
a small  mica  screen  coated  with  lithium  chloride,  different  regions 
of  the  tube  can  thus  be  investigated. 

O.H.  Smith3  investigated  the  retrograde  rays  from  a cold  cath- 
ode, measuring  t efle  ns  by  . eans  of  the  t ..  on  a photo- 

graphic plate.  He  found  that  for  retrograde  rays  in  residual  air 
the  hydrogen  molecule  appeared  on  every  plate,  accompanied  by  a 
heavier  carrier  which  in  most  cases  was  the  oxygen  molecule;  that 
the  negative  lines  were  sharper  and  clearer  than  the  positive  lines 
— probably  because  of  the  disturbance  of  the  path  of  the  positive 
ion  in  becoming  positive;  that  retrograde  rays  could  be  produced 
with  a cathode  having  a bore  in  the  canal  as  small  as  .05  mm.  in 
diameter;  that  the  best  range  of  pressures  was  from  .008  to  .015  mm. 
of  mercury;  and  finally,  that  the  power  of  a moving  particle  to  af- 
fect a photographic  plate  seemed  to  be  a function  of  its  kinetic 
energy. 

The  mere  sensitive  methods  that  have  recently  been  developed 
for  the  investigation  of  positive  rays  might  well  be  applied. in  the 
investigation  of  retrograde  rays. 


* J.J.  Thomson,  Rays  of  Positive  Electricity. 

2 O.H.  Smith,  Phys. Review,  7,  pp  635-633,  June  1916. 


. 


. 


. 


. 


. 


. . 

. . 


4 


II.  METHODS  OF  PRODUCING  RETROGRADE  RAYS 

The  type  cf  cathode  used  determines,  to  a -great  extent,  the  in- 
tensity of  the  beam  produced;  sc  does  also  the  shape  of  the  discharg 
tube.  A double  cathode  made  cf  t . _ . ..dial  triangular  plates,  or 
one  made  of  a wire  gauze,  give  rich  sources  of  retrograde  rays  — 
though  in  any  case  they  are  weak  in  comparison  with  the  canal  rays. 

A hollow  cylindrical  cathode,  having  the  ends  closed  with  discs 
Which  have  - all  central  apertures  or  slits,  gives  a rich  source  of 
positive  rays,  and  also  of  retrograde  rays. 

The  shape  cf  the  discharge  tube,  due  to  the  electrostatic  in- 
fluence cf  the  walls,  is  a deciding  factor  in  the  definition  or  con- 
centration cf  the  beam  produced. 

III.  THE  APPARATUS 

A,  The  Discharge  Tube  Proper.-  The  tube  was  made  of  pyres  glaa 


and  was  the  so-called  "dumb-bell”  type  developed  by  ICnipp  and  Kunz, 
It  consisted  essentially  of  two  bulbs,  made  .from  1.5  liter  flasks, 
joined  together  by  a tuoe  in  the  center  cf  which  was  a hollow, 
cylindrical  cathode,  K,  (Plate  I).  The  outer  tube,  T^,  joining 
the  two  bulbs  and  Ag,  was  36  cms.  long  by  4.3  cms.  diameter. 

The  inner  tube.  To,  was  sealed  in  by  the  ring  seal,  S,  and  was  ex- 


actly concentric  with  the  outer  tube.  This  inner  tube  was  10  cms. 
long  by  3 cms.  in  diameter,  and  was  drawn  in  at  n so  that  the  cath- 
ode was  held  concentric  within  the  tube.  The  purpose  of  this  in 
tube  was  to  get  the  face  of  the  cathode  nearly  flush  with  the  walls 
of  the  neck  cf  the  tube,  which  has  been  shewn  to  be  the  best  condi- 


tion for  a concentrated  beam  (J.J.  Thomson,—  Rays  of  Positive  Elec- 
tricity). The  large  ground  joint,  Jg,  permitted  the  removal  cf  b 


5 

bulb  A p,  thereby  givii  ?o  ess  to  the  cathode.  By  removing 
cat  hods  . inal  plug  fro,:  the  ground  joint,  J„,  and  unscr  vi  ig  the 
stem  from  the  cathode,  the  cathode  could  be  removed  and  be  replaced 
by  another  — or  any  other  changes  made.  The  stem  which  held  the 
cathode  in  place  as  enclosed  by  a small  glass  tube,  as  may  be  seen 
in  the  diagram.  An  anode  was  sealed  into  each  bulb  hy  means  of 
tungsten  seals  through  special  intermediate  ^lass  so  that  the  retro- 
grade rays  could  be  formed  in  either  side  cf  the  tube  at  will. 
was  a charcoal  bulb  for  removing  all  absorbable  gasses.  The  small 
tube,  P]_,  for  priming,  and  the  stop  cook,  Q.p,  for  shutting  the  tube 
off  from  the  exhaust  system,  are  shown  in  Plate  II. 

E.  The  Exhaust  Line  and  Pumping  System.-  The  connection  of  the 
tube  proper  through  the  exhaust  line  to  the  pumping  system  is  shown 
by  Plate  II.  This  unit  .-.as  connected  t 

ground  point,  J3.  QP  was  a stop  cock  for  shutting  off  the  pumps 
from  the  rest  of  the  system  while  the  tube  was  beii  primed.  The 
liquid  air  trap,  B3,  prevented  any  mercury  vapor  from  entering  the 
system  from  the  pump.  The  phosphorous  pent  oxide  bulb,  B^.,  removed 
all  ...  - the  system,  while  the  chare  , 

•W 

moved  all  absorbable  gasses  during  the  process  of  priming  the  tube. 
Pg  was  a capillary  stem  for  letting  down  the  vacuum  in  the  system. 

C.  The  C.  . _ai  tne  Anodes.-  The  cathode  was  made  entirely 

of  aluminum,  being  the  hollow,  cylindrical  type.  Plate  III  shows 
■ - construction.  The  drawing  represents  the  cathode  twice  actual 
size  in  order  to  show  the  construction  more  clearly.  The  discs 
were  wedged  into  the  channeled  ends.  The  small  door  was  mounted  as 
shown  in  section,  b limensions  and  construction  ing  such  that 
the  door  was  well  balanced.  After  oeing  closed  by  tilting  tne  tube 


h?v/V/V/y/w,i 


it  just  remained  closed  when  the  tube  was  in  a horizontal  position, 
and  could  be  opened  by  tilting  the  tube  into  a vertical  position. 
The  mounting'  of  the  tube,  and  the  joint  J-,  permitted  the  opening 
and  closing  of  this  doer  even  while  the  tube  was  being  evacuated. 
The  dimensions  of  the  cathode  were  as  follows: 


Outer  cylinder:  length  ; 

diameter  (outer) 3.54  cm. 

Inner  cylinder:  length  l.g 

diameter  (out .r) 3.38  cm. 

imeter  of  apertures 


The  anodes  were  made  of  small  aluminum  rods  sealed  through  the 
glass  with  tungsten.  A bead  of  special  Corning  glass  was  first 
formed  upon  the  tungsten  wire.  To  this  bead  was  fused- a short  tube 

■ m3  ) . 

glass  was  then  fused  onto  the  the  anode. 

The  terminal  for  the  cathode  was  a plain  platinum  seal  through  the 
common  glass  of  the  terminal  plug.  The  tips  of  ail  the  electrodes 
were  protected  by  placing  corks  over  them,  and  joining  on  flexible  i 
copper  leads  made  of -several  strands  of  fine  wire. 

• cem . — The  bulb  whi  contained  the  suj 

of  helium,  and  the  system  of  stop  cocks  for  letting  small  quantities 

out  , are  shown  in  Plate  IV.  was  joined  to  P^  through 

a capillary  tube  for  sealing  off. 

>pe.  - r constant  deviation  -spectr  - 

scope,  irith  an  illuminated  pointer  eve-piece  was  used  in  makin-  the 
observations. 


7 


IV.  MANIPULATION 

A.  Mounting  the  Tube.-  Photograph  II  shows  the  general  set-up 
of  the  apparatus  for  priming  the  tube,  The  mounting  was  so  made 
that  the  tube  could  be  turned  in  order  to  open  or  close  the  small 

sathode  during  the  process  of  exhaustion.  It  shoul 
be  noted  also  that  sufficient  flexibility  was  allowed  to  r> revent  toe 
much  strain  on  the  ground  joint.,  J3.  This  flexibility  was  obtained 
by  suspending  the  unit  shown  in  Plate  II  by  means  of  a spring  sus- 
pension. 

B.  Procedure  for  Priming.-  A Xnipp  mercury  vapor  pump , support 

ed  by  a Cenco-Nelscn  Hyvao  oil  pump,  was  used  to  pump  out  the  sys- 
tem. Before  introducing  helium  into  the  tube,  the  pumps  were  al- 
lowed to  run  several  hours,  and  at  tne  same  time  both  of  the  char- 
coal bulbs.  Bn  and  B2,  were  heated  with  Bunsen  burners  to  drive  out 
all  occluded  gasses.  In  heat.in  larcoal  bulbs,  care  was  taken 

net  to  get  them  too  hot  and  soften  the  glass.  All  lubricated  joints 
were  carefully  protected  from  the  heat  by  asbestos.  The  mercury 
vapor  pump  was  put  into  operation  only  after  the  oil  pump  had 
reached  its  limit.  At  all  times  when  the  mercury  vapor  pump  was  in 
operation,  liquid  air  was  kept  on  the  trap,  B3,  to  prevent  any  mer- 
cury vapor  from  entering  the  tube  from  the  pump. 

Now,  wit  Q Qg,  and  Qg  closed,  the  tube  was  thoroughly  out- 
gassed,  and  the  mercury  vapor  pump  all  to  carry  ti  acuum  to 

hj  ainable  point.  Then  CV,  was  closed,  t,:  at  removed 

from  Bg,  and  the  pumps  were  stopped.  The  ap]  cat us  was  then  ready 
for  the  introduction  of  the  helium.  This  was  done  as  follows:  Q5 
was  opened  for  a moment  and  then  closed.  Q4  ".'as  next  , al- 

lowing a "dose”  of  helium  to  pass  into  the  tu  >e.  Q4  was  then  closed 


II 


— — 


8 

again.  The  quantity  cl’  helium  introduced  was  regulated  by  the  numb s ! 
of  Mdses”  g . ext,  liquid  air  was  put  on  Bg,  and  B|  ■ t ed 

more.  Bg  removed  all  impurities  from  the  helium,  while  the  phos- 
phorous pent oxide  bulb,  B4,  removed  all  water  vapor.  When  the  posi- 
tive rays  appe  quite  red,  was  closed,  the  heat  removed  from 
q,  and  the  ao.i  from  By. 

- xt  was  closed,  and  the  priming  unit  sealed  c ff  at  P^P<. 

- ■ . with  fairly  purs,  dry  helium. 

C*  i'c^ai ay  tne  Qb s ervat  10ns . - The  Hilger  cons 
spectroscope  was  used.  Some  of  one  readings  • - 

direct,  as  indicated,  and  the  others  were  made  by  focussing  the  de-  1 
sired  beam  by  a lens  and  casting  a sharp  image  upon  the  slit.  This  ! 
gave  brighter  lines.  Many  of  the  lines  were  too  faint  to  make  accu- 
rate observations. 


. 

* 

* 


. 


. 


V.  DATA 


A.  Ob  s srvat  i one . - 


I.  Positive  ray  viewed  lengthwise  with  the 

slit  of  the  cathode 

focussed  upon 

the  slit  of 

the  spectroscope: 

o 

A units 

color 

Intensity  Standard 

Element 

6710 

red 

F 6708  ? 

Li  ? 

5880 

yellow 

VE  5890 

Na 

5047 

green 

VF  5847,8 

He 

5017 

green 

VB  5015, 7 

He 

4833 

green 

F 4833 

He 

4713 

blue 

VF  4713 

He 

4471 

violet 

VF  4471,6 

He 

4387 

violet 

VF  4388 

He 

Ii.  Cathode  ray  - viewed  lengthwise  with  th 

e slit  of  the  oath- 

ode 

focussed  upon  the  slit 

of  the  spectroscope: 

6711 

V 

5890 

VE 

5043 

VF 

5016 

VB 

4931 

B 

4711 

VF 

4470 

F 

4388 

VVF 

III.  netrograde  ray  - 

viewed  diagonally,  cathode  ray  deflected. 

tne 

retrograde 

ray  being 

focussed  upon  the  slit 

of  the  spectroscope 

5830 

F 

504S 

VF 

5013 

B 

4919 

F 

4709 

VVF 

4470 

F 

IV.  Undeflect e&  Cathode  Hay  - viewed  sidewise,  and  direct  with-! 

out 

focussing 

lens: 

5890 

B 

5053 

VF 

5015 

B 

4323 

VF 

4711 

VVF 

4471 

VVF 

. 


. 


. 


. 


10 


V.  Retrograde  ray  - viewed  side-wise,  cathode  ray  deflected,  an 
direct  without  focussing  lens; 


5890 

VF 

5017 

B 

4S21 

VF 

4731 

VVVF 

VI.  Positive  ray  - 

viewed  side- 

and  direct  without  focussing  lens: 

5890 

F 

5014 

B 

4933 

VF 

4465 

VVF 

VII.  Cathode  1 

■ viewed  siae^ 

of  the  spectroscope: 

58S0 

B 

5051 

VF 

5017 

VB 

4921 

F 

4863 

VVF 

4712 

VF 

4471 

B 

4388 

VF 

VIII.  Positive  ray 

- viewed  sid< 

ed,  focussed  upon  the  slit  of  the  sp 

58S0 

B 

5048 

VVF 

5015 

VB 

4331 

VF 

47X3 

VVF 

4468 

VF 

E . Table  for  Coin-far  is  on.  - 


I 

II 

III 

IV 

V 

VI 

VII 

VIII 

C ol  or 

El ement 

6710 

6711 

— 

— 

■ 

red 

Li? 

5830 

5890 

5890 

5830 

5890 

5890 

5890 

5830 

yellow 

Na? 

5047 

5049 

5049 

5052 

- — — 

5051 

5048 

green 

He 

5017 

5016 

5013 

5015 

5017 

5014 

5017 

5015 

green 

He 

4932 

4921 

4313 

4922 

4331 

4922 

4931 

4921 

gr  een 

He 

4713 

4711 

4709 

4711 

4730 

— 

4712 

4712 

blue 

He 

4471 

4470 

4470 

4471 

— 

446  5_ 

4471 

4468 

v i ol  et 

He 

4387 

4388 

— 

4388 

vi  olet 

He 

I. 

Positive 

ray  - 

v i ew ed 

lengt 

hwise 

with  the  slit 

of  the  * 

ode  focussed  upon  the  slit  of  the  spectroscope: 

II.  Cathode  ray  - viewed  lengthwise  with  the  slit  of  the  cath- 
ode focussed  upon  the  slit  of  the  spectroscope: 

III.  Retrograde  ray  - viewed  diagonally,  cathode  ray  deflected, 
the  retrograde  ray  being  focussed  upon  the  slit  of  the  spectroscope:, 

IV.  Undeflected  Cathode  ray  - viewed  sidewise,  ai 
out  focussing  lens: 

V.  Retrograde  ray  - viewed  side-wise,  cathode  ray  deflected, 
and  direct  without  focussing  lens: 

VI.  Positive  ray  - viewed  side-wise,  negative  ray  undeflected, 
and  direct  without  focussing  lens: 

VII.  Cati . glow  - viewed  side-wise,  focussed  upon  the  slit 
of  the  spectroscope: 

VIII.  Positive  ray  - viewed  side-wise,  negative  rays  undeflect- 
ed, focussed  upon  the  slit  of  the  spectroscope: 


■ 


. 


' 

. 


‘ 


■ 


13 


VI.  CONCLUSIONS 

The  chief  difficulty  in  making  this  investigation  was  to  get  a 
Learn  intense  enough  to  give  a bright  spectrum,  in  order  to  make  ac- 
iings.  From  the  very  nature  of  the  rays  and  the  manner  in 
which  they  are  produced  it  is  impossible  to  get  a ray  nearly  so  in- 
tense as  the  positive  ray.  Much  time  was  spent  trying  to  get  an  in- 
tense beam,  by  varying  the  quantity  of  helium.  Too  much  helium  caus 
es  diffused  rays  which  mask  the  retrograde  ray,  while  too  little 
does  net  give  a distinct  beam.  In  the  tube  finally  used  the  beam 
extended  about  three-fourths  of  the  way  across  the  bulb,  and  the 
bulb  was  fairly  clear  from  diffuse  and  reflect  ays. 

To  the  naked  eye  the  beam  of  the  positive  ray  and  of  the  retro- 
grade ray  appeared  slightly  different,  the  latter  appearing  a mere 
purplish  tinge. than  the  former.  The  writer  thinks  this  was  due  to 
the  difference  in  the  intensity  of  the  two  beams. 

All  the  observations  showed  distinctly  the  yellow  sodium  line 
(5890). 

In  the  two  observations  where  the  inside  of  the  cathode  was  fo- 
cussed on  the  slit  a red  line,  apparently  lithium,  appeared.  This 
must  be  due  to  phosphorescence  on  a slight  amount  of  impurity  of 
lithium. 

In  all,  seven  different  helium  lines  appeared,  while  for  the 
retrograde  rays  only  three  were  present.  Those  lines  not  present 
for  tne  retro  - / ray  were  faint  lines  i the  other  observations. 

All  of  the  lines  that  were  present  in  the  retrograde  ray  were 
also  present  in  the  positive  ray. 

In  conclusion,  I wish  to  express  my  appreciation  to  Professor 
C.T.  Knlpp  for  the  interest  and  assistance  given  in  this 


" 


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■ 

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I ifl  ' a 1 


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investigation  and  ^Isc  to  thank  Professor  A.P.  c . ..  for  the  facili 

ties  of  the  laboratory. 


__ 

— 


UNIVERSITY  OF  ILLINOIS-URBANA 


3 0112 108856573 


